I didn't get the beginning

Rating: Null/10 (28 April 2004)

What are all those riots in the opening scenes of 28 Days Later? I thought they were the panic about the disease, but then they show the monkey in the lab and it looks like the monkey's escape is what starts the spread of the virus. Which comes first: that monkey's escape or the spread of the virus?
If the monkey's escape happens after the spread and the panic, why are those animal rights activists bothering with monkeys when the world is all going to hell? If the monkey's escape happens after the spread and the panic, why are those animal rights activists bothering with monkeys when the world is all going to hell?